Window casing

ABSTRACT

A system and method for perforating and fracturing at least one of a casing or a sleeve proximate to the casing in a wellbore are perforated to form one or more apertures therein. The apertures are operable to allow passage of fluids between an interior of the casing and earth surrounding the wellbore. The earth surrounding the wellbore can be fractured through the apertures. The sleeve can be moved to selectively close one or more of the apertures and substantially seal against passage of fluids therethrough.

This disclosure relates to selectively accessing formations surrounding wellbores.

After a wellbore is drilled, the wellbore is often treated by perforating and fracturing to increase the flow of fluids from the formation into the wellbore. Perforating entails forming holes in the walls of the wellbore, for example the casing, to enable the formation around the wellbore to be fractured. Fracturing entails inducing fractures in the formation surrounding the wellbore.

Perforating is generally performed with a perforating tool that is lowered into the wellbore on a wireline or a coiled or jointed tubing string. There are a number methods by which to perforate a wellbore. One method includes utilizing a jetting-type perforating tool through which a fluid passes at a pressure high enough to cut openings, or perforate the wall of a wellbore. Another method includes utilizing a shaped charge-type perforating tool that uses a directional explosive effect to generate a high pressure, high velocity jet that creates an opening or a perforation in the wall of a wellbore. Yet another method includes utilizing a projectile-type perforating tool that fires a bullet or projectile into the wall of the wellbore to create an opening or a perforation therein.

Fracturing is generally performed by sealing an interval within the wellbore, for example between two packers on a working string or between a bridge plug and a seal, such as a packer or a BOP, at the surface, and pressurizing the wellbore within the sealed interval to induce fractures in the formation surrounding the formation. The perforations allow the pressurized fracturing fluid to enter the formation.

Once the casing has been fractured, however, there is a direct communication between the fracture and the wellbore. Should this fracture produce sand, as is common with most less consolidated formations, the sand will be produced through the perforations to the surface, and may abrade or otherwise damage surface equipment.

SUMMARY

The present disclosure is directed to systems and methods for selectively accessing formations surrounding wellbores. Certain aspects enable closure of perforations in a casing of the wellbore before and after fracturing has been performed.

One aspect encompasses a method. In the method at least one of a casing or a sleeve proximate to the casing in a wellbore are perforated to form one or more apertures therein. The apertures are operable to allow passage of fluids between an interior of the casing and earth surrounding the wellbore. The sleeve is moved to close one or more of the apertures and substantially seal against passage of fluids therethrough.

Another aspect encompasses method of perforating and fracturing a well. In the method one or more perforations are formed through a casing of the well. Fluid is flowed through one or more of the perforations to fracture a formation about the well. At least one of the perforations are closed to substantially seal against passage of fluids therethrough.

Yet another aspect encompasses a well completion system. The system includes a casing adapted for insertion into the well. A downhole tool is adapted for insertion into the casing and operable to form one or more perforations through the casing. The one or more perforations are adapted to allow passage of fluid through the casing. A sleeve is carried by the casing and movable to cover and substantially prevent passage of fluid through one or more of the perforations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of an illustrative well constructed according to the concepts described herein.

FIGS. 2A-2D are schematic cross-sectional views of an illustrative window casing system according to the concepts described herein. FIG. 2A depicts the illustrative window casing in a closed position prior to perforating and fracturing. FIG. 2B depicts the illustrative window casing in an open position and receiving an illustrative working string to perforate the window casing. FIG. 2C depicts the window casing in an open position during fracturing. FIG. 2D depicts the window casing and a closed position after perforating and fracturing.

FIG. 3 is schematic cross-sectional view of the illustrative window casing receiving an alternate illustrative working string according to the concepts described herein.

FIG. 4 is a schematic cylindrical projection of an illustrative cam slot according to the concepts described herein.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

Referring first to FIG. 1, an illustrative well system 10 constructed in accordance with the concepts described herein includes a wellbore 12 coupled to the surface 14 and extending down through the earth 16. The wellbore 12 may extend substantially vertically away from the surface, as is depicted in FIG. 1, or may deviate to extend at any angle from the surface 14. In some instances, for example, the entire wellbore 12 or portions thereof may be slanted, horizontal, and/or curved. The wellbore 12 extends through one or more (three shown) intervals of interest 18. The intervals of interest 18 are intervals of the earth 16 in which it is desired to produce fluids, inject fluids, or perform other operations. An interval of interest 18 may correspond to a single formation in the earth 16, may span multiple formations, or may encompass only a portion of a formation.

A casing 22 extends through at least portion of the wellbore 12. The casing 22 includes one or more longitudinally spaced window casings 24. A window casing 24 is a section of casing configured to enable selective access to the earth 16 surrounding the wellbore 12. One or more window casings 24 may be provided in each of the intervals of interest 18.

Although there are numerous configurations of window casing 24 that can be used according to the concepts described herein, an illustrative window casing 200 is depicted in FIGS. 2A-2D. Referring specifically to FIG. 2A, illustrative window casing 200 includes a substantially cylindrical outer casing 210 that receives a moveable sleeve member 212. The outer casing 210 can define a recess 214 in which the sleeve member 212 resides. In the illustrative window casing 200, the recess 214 is configured to allow the sleeve member 212 to slide axially relative to the outer casing 210. In other instances, the sleeve member 212 can alternately, or in combination with sliding axially, be configured to rotate within the outer casing 210.

Referring now to FIGS. 2A and 2B, the sleeve member 212 is provided with one or more apertures 216. Some or all of the apertures 216 can be formed prior to placement of the illustrative window casing 200 in the wellbore 12, and the remainder or all of the apertures 216 can be formed after placing the illustrative window casing 200 in the wellbore 12 (discussed in more detail below). Likewise, the outer casing 210 is provided with one or more apertures 218, formed prior to and/or after placement of the illustrative window casing 200 in the wellbore 12. When the apertures 218 of the sleeve member 212 at least partially overlap the apertures 218 of the outer casing 210, the fluid may pass through the illustrative window casing 200, and more specifically, between the interior of the sleeve member 212 and the earth 16.

The sleeve member 212 is movable between an open position and a closed position. The open position corresponds to the position of the sleeve member 212 that allows passage of fluid through the illustrative window casing 200, and the closed position corresponds to the position of the sleeve member 212 that substantially seals against passage of fluid through the illustrative window casing 200. FIGS. 2B and 2C depict the sleeve member 212 in the open position, shifted to abut the upper end of the recess 214. In the open position, apertures 216 and apertures 218 at least partially overlap. FIGS. 2A and 2D depict the sleeve member 212 in the closed position, shifted to about the lower end of the recess 214. In the closed position, apertures 216 and apertures 218 do not overlap. Additionally, a plurality of seal members 220 substantially seal against passage of fluid between the apertures 216 and 218. In the illustrative window casing 200, the seal members 220 are positioned on the outer surface of the sleeve member 212 and are configured to substantially seal against passage of fluid between the sleeve member 212 and the outer casing 210. In other instances, some or all of the seal members 220 can be provided on the outer casing 210 itself and configured to substantially seal against the sleeve member 212.

The sleeve member 212 is moved between the open and closed position with a sleeve operating tool. Although there are numerous configurations of sleeve operating tools that can be used according to the concepts described herein, an illustrative sleeve operating tool 222 is depicted in FIGS. 2B-2D (best seen in FIG. 2D). The illustrative sleeve operating tool 222 is adapted to be coupled to a working string 224 and lowered through the wellbore 12 into the interior of the sleeve member 212. The illustrative sleeve operating tool 222 may also be adapted to couple to or carry other devices, for example, a tool for forming apertures 216 and/or apertures 218 such as illustrative hydraulic jet stub 226 (described in more detail below).

The illustrative sleeve operating tool 222 includes a tool body 228 that carries one or more outwardly extendable collets 230. The collets 230 are configured to engage a corresponding profile 232 on the sleeve member 212 when extended outwardly into engagement with the profile 232, and move the sleeve member 212 as the illustrative sleeve operating tool 222 is itself moved. In one instance, the collets 230 are inwardly biased and driven outward as they bear against a wedge surface 234 on the tool body 228. When not outwardly extended (i.e. retracted), the collets 230 are positioned to lightly engage and easily release the profile 232 without substantially moving the sleeve member 212. The illustrative sleeve operating tool 222 includes two axially spaced sets of collets 230 coupled to a carrier 236. The carrier 236 is received over the tool body 228 and configured to both slide axially and rotate on the tool body 228. The tool body 228 also includes two axially spaced wedge surfaces 234. Each wedge surface 234 is oriented to slope outward and away from the other wedge surface, so that when the carrier 236 is shifted towards one or the other wedge surface 234, the collets 230 that contact the wedge surface 234 are wedged outward. Because the collets 230 lightly engage the profile 232 when not outwardly extended, the collets 230 on the leading edge of the carrier 236 pass over the profile 232 as the illustrative sleeve operating tool 222 is passed through the sleeve member 212. The collets 230 on the trailing edge of the carrier 236 will engage the profile 232 and drag the carrier 236 toward the corresponding wedge surface 234. As the illustrative sleeve operating tool 222 continues into the sleeve member 212, the wedge surface 234 drives the collets 230 on the trailing edge into further engagement with the profile 232, and thereafter draws the sleeve member 212 along with illustrative sleeve operating tool 222.

Accordingly, to move the sleeve member 212 from the open position to the closed position, the illustrative sleeve operating tool 222 is lowered downward through the illustrative window casing 200. The collets 230 on the leading end pass over the profile 232. The collets 230 on the trailing end lightly engage the profile 232 and draw the carrier 236 toward the trailing wedge surface 234. The trailing wedge surface 234 wedges the collets 230 into more positive engagement with the profile 232, and further downward movement draws the sleeve member 212 along with the illustrative sleeve operating tool 222 to the closed position. To move the sleeve member 212 from the closed position to the open position, the illustrative sleeve operating tool 222 is lowered downward through the illustrative window casing 200 (if not already below the illustrative window casing 200) and then withdrawn upward through the illustrative window casing 200. As above, the collets 230 on the leading end pass over the profile 232. The collets 230 on the trailing end lightly engage the profile 232 and draw the carrier 236 toward the trailing wedge surface 234. The trailing wedge surface 234 wedges the collets 230 into more positive engagement with the profile 232, and further upward movement draws the sleeve member 212 along with the illustrative sleeve operating tool 222 to the open position.

The tool body 228 has one or more cam slots 238 that receive one or more corresponding pins 240 on the carrier 236. The cam slot 238 and pin 240 control the movement of the carrier 236, and thus whether the collets 230 can extend, engage and move sleeve member 212. FIG. 4 depicts a cylindrical projection of an illustrative cam slot 238. The illustrative cam slot 238 has a plurality of trapezoidal neutral receptacles 242, a closed position receptacle 244, and an open position receptacle 246 (two shown). Additional or fewer closed position receptacles 244, open position receptacles 246 or neutral receptacles 242 can be provided, for example, to achieve desired operation of the carrier 236 or accommodate additional or fewer pins 240. The neutral receptacles 242, closed position receptacle 244 and open position receptacles 246 are coupled to one another to allow the pins 240 to traverse between the receptacles. The closed position receptacle 244 extends axially outward from the neutral receptacles 242 in one direction, and the open position receptacles 246 extend axially outward from the neutral receptacles 242 in an opposite direction. In the illustrative sleeve operating tool 222, the closed position receptacle 244 extends upward, and the open position receptacles 246 extend downward.

With the pin 240 received in any of the neutral receptacles 242, the carrier 236 is retained relative to the tool body 228 so that the collets 230 cannot engage either wedge surface 234. Accordingly, the illustrative sleeve operating tool 222 can pass through the window casing 200 without opening or closing the sleeve member 212. With the pin 240 received in the closed position receptacle 244, the carrier 236 can move to wedge the collets 230 on the upper wedge surface 234 into engagement with the profile 232 when the illustrative sleeve operating tool 222 is moved downward through the sleeve member 212. With the pin 240 received in the open position receptacle 246, the carrier 236 can move to wedge the collets 230 on the lower wedge surface 234 into the profile 232 as the illustrative sleeve operating tool 222 is moved upward through the sleeve member 212.

Each time the illustrative sleeve operating tool 222 passes through the sleeve member 212, the pin 242 moves to an adjacent receptacle (neutral receptacle 242, open position receptacle 246, or closed position receptacle 244). Accordingly, the illustrative sleeve operating tool 222 can be selectively configured to change the sleeve member 212 to the open position, change the sleeve member 212 to the closed position or pass through the illustrative window casing 212 without changing the position of the sleeve member 212 by alternately passing the sleeve operating tool 222 through the sleeve member 212. For example, if the pin 240 is received in the first open position receptacle 246 (at the top right of FIG. 4), the pin 240 can be moved to a neutral receptacle 242 by passing the illustrative sleeve operating tool 222 downward through the sleeve member 212. As noted above, with the pin 240 in a neutral receptacle 242, the sleeve operating tool 222 can pass through the sleeve member 212 without changing its position. By passing the sleeve operating tool 222 upward and then back downward through the sleeve member 212, the pin 240 is then moved to the closed position receptacle 244. As noted above, with the pin 240 in the closed position receptacle 244, the sleeve operating tool 222 will move the sleeve member 212 to the closed position when it passes downward through the sleeve member 212. By passing the sleeve operating tool 222 upward through the sleeve member 212, the pin 240 is moved to another neutral receptacle 242. By passing the sleeve operating tool 222 downward and then upward through the sleeve member 212, the pin 240 can be moved to another open position receptacle 246. As discussed above, with the pin 240 in an open position receptacle 246, the sleeve operating tool 222 will move the sleeve member 212 to the open position when it passes upward through the sleeve member 212.

Referring back to FIG. 2B, if at least some of the apertures 216 or apertures 218 are to be formed with the illustrative window casing 200 in the wellbore 12, the working string 224 includes a device to form the apertures. In one instance, the device is hydraulic jet sub 226. In one instance, the hydraulic jet sub 226 is a jet sub similar to that described in U.S. Pat. No. 5,765,642. In other instances, the device can be a shaped charge, projectile or other perforating device. The hydraulic jet sub 226 is a device configured to direct high pressure fluid radially outward to perforate (i.e. form apertures in) the wall of the wellbore 12, including casing 22 and illustrative window casing 200. To this end, the hydraulic jet sub 226 includes a body 248 adapted to couple to the illustrative sleeve operating tool 222, and the body 248 has one or more radially oriented ports 250 spaced about its circumference. In one instance, the ports 250 may be nozzles configured to consolidate and direct flow from the interior of the hydraulic jet sub 226 into the wall of the wellbore 12. It is within the scope of the invention to use other types of devices for forming apertures, in combination with or in lieu of the hydraulic jet sub 226, to perforate the wall of the wellbore 12, for example, a projectile perforating gun, shaped charge perforating gun, or other system.

As is discussed in more detail below, the hydraulic jet sub 226 is operated to perforate at least one of the outer casing 210 (forming apertures 218) or the sleeve member 212 (forming apertures 216). In certain embodiments, the ports 250 of the hydraulic jet sub 226 are positioned about the body 248 such that when the hydraulic jet sub 226 is coupled to the illustrative sleeve operating tool 222, and the collets 230 on the upper end of the illustrative sleeve operating tool 222 engage the profile 232 of the sleeve member 212 in the open position, the hydraulic jet sub 226 forms the apertures 216 and apertures 218 between the seal members 220.

With the sleeve member 212 in the open position, the earth 16 surrounding the wellbore 12 may be fractured by introducing high pressure fracturing fluid into the wellbore 12 to flow through the apertures 216 and apertures 218 and into the earth 16. The fracturing fluid can be communicated to the vicinity of the apertures 216 and apertures 218 in numerous ways. For example, the fracturing fluid can be communicated to the vicinity of the apertures 216 and apertures 218 entirely through the annulus between working string 224 and the wall of the wellbore 12 (e.g., casing 22). In other instances, at least a portion of the fracturing fluid can be communicated to the vicinity of the apertures 216 and apertures 218 through the interior of the working string 224. FIG. 2C depicts the fracturing fluid flowing (represented by arrows 254) through both the working string 224 and through the annulus between the working string 224 and the wall of the wellbore 12. In this instance, the fracturing fluid exits the interior of the working string 224 through ports 250 of the hydraulic jet sub 226. The flow of fracturing fluid out of ports 250 into the perforations 252 creates a pressure gradient that draws the fracturing fluid from the annulus between the working string 224 and the wall of the wellbore 12 into the perforations 252. The combined flow from the annulus and from the hydraulic jet sub 226 fractures the earth 16 through the apertures 216 and apertures 218.

Although, it is within the scope of the invention to direct all of the fracturing fluid through the working string 224 and out the ports 250, it is many times difficult to configure the ports 250 to both operate efficiently in perforating the wall of the wellbore 12 and efficiently communicate the flow rate and withstand the erosive effects of the volume of fracturing fluid (including proppant) necessary to fracture the earth 16. FIG. 3 depicts an alternate configuration in which the working string 224 includes a fluid distributor 256 changeable from directing flow axially through the fluid distributor 256 to directing flow both axially through the fluid distributor 256 and laterally through one or more side ports 258 in the working string 224. When the fluid distributor 256 is configured to direct flow axially through the fluid distributor 256, flow from the interior of the working string 224 is directed to the hydraulic jet sub 226. Therefore, during perforating operations with the hydraulic jet sub 226, the fluid distributor 256 can be configured to direct flow axially through the fluid distributor 256 into the interior of the hydraulic jet sub 226 and perforating operations performed substantially as described above. During fracturing operations, the fluid distributor 256 can be configured to direct flow both axially through the fluid distributor 256 and laterally through the side ports 258. At least a portion of the flow of fracturing fluid through the side ports 258 is directed into the annulus between the working string 224 and the wall of the wellbore 12. In one instance, a majority of the fracturing fluid is directed through the side ports 258. The side ports 258 may be configured to be less of a flow restriction than the ports 250 of the hydraulic jet sub 226. Further, diverting a portion of the flow through the side ports 258 reduces the amount of flow through the ports 250 of the hydraulic jet sub 226.

An illustrative method of perforating and fracturing a wellbore according to the sequence of operations depicted in FIGS. 2A-C will now be discussed. In the illustrative method, the working string 224 including the illustrative sleeve operating tool 222 and hydraulic jet sub 226 is lowered through the wellbore 12 into the vicinity of an illustrative window casing 200. Perforating and/or fracturing operations can be performed at more than one illustrative window casing 200 during a single trip of the working string 224 into and out of the wellbore 12. If perforating and/or fracturing operations are to be performed at multiple illustrative window casings 200, the working string 224 can be lowered through the wellbore 12 into the vicinity of the illustrative window casing 200 furthest from the surface 14, perforating and/or fracturing operations performed at the illustrative window casing 200 as described herein, the working string 224 drawn up the wellbore 12 to the next illustrative window casing 200 to be perforated and/or fractured (not all illustrative window casings 200 in a wellbore 12 must be perforated or fractured), and so on. In other words, the operations can be performed in illustrative window casings 200 sequentially from the bottom of the wellbore 12 up. Alternately, the operations can be performed in illustrative window casings 200 sequentially from the surface 14 towards the bottom of the wellbore 12, or in any other order or in no specific order.

In FIG. 2A the illustrative window casing 200 is shown installed with the sleeve member 212 in the closed position. However, it is within the scope of the invention to install the illustrative window casing 200 with the sleeve member 212 in the open position (the open position shown in FIG. 2B). If the sleeve member 212 is in the closed position, the illustrative sleeve operating tool 222 is configured to move the sleeve member 212 to the open position. To this end, the collets 230 on the lower end of the carrier 236 reside adjacent the lower wedge surface 234. The illustrative sleeve operating tool 222 is lowered through the sleeve member 212 so that the collets 230 on the lower end of the carrier 236 pass downward past the profile 232 on the sleeve member 212. The illustrative sleeve operating tool 222 is then drawn back up through the sleeve member 212, so that the collets 230 lightly engage the profile 232. Further upward movement wedges the collets 203 against the lower wedge surface 234, more positively engages the collets 230 in the profile 232, and draws the sleeve member 212 to the open position. With the collets 230 on the lower end of the carrier 236 engaged in the profile 232 and the sleeve member 212 in the open position, the ports 250 of the hydraulic jet sub 226 are aligned between the seal members 220.

Referring to FIG. 2B, the hydraulic jet stub 226 is actuated to perforate the outer casing 210 and the sleeve member 212, thus forming one or more apertures 216 and apertures 218. The hydraulic jet sub 226 is actuated by supplying high pressure fluid down the interior of the working string 224 and out the ports 250. In some instances, the perforations 252 can extend into the earth 16.

The earth 16 surrounding the wellbore 12 may be fractured by introducing high pressure fracturing fluid into the wellbore 12 to flow through the apertures 216 and apertures 218 (whether formed by perforating as described above or provided prior to installation) and into the earth 16. As discussed above, the fracturing fluid can be communicated to the vicinity of the apertures 216 and 218 in a number of ways. FIG. 2C depicts the fracturing fluid flowing (represented by arrows 254) through both the annulus between the working string 224 and the wall of the wellbore 12 and through the working string 224 and out of the ports 250. FIG. 3 depicts the fracturing fluid flowing through the working string 224, a portion of the fluid being diverted by the fluid distributor 256 through side ports 258, and a portion of the fluid flowing axially through the working string 224 into the hydraulic jet sub 226 and exiting a ports 250 thereof. The flow of fracturing fluid out of the ports 250 into the earth 16 creates a pressure gradient that draws the fracturing fluid from the annulus between the working string 224 and the wall of the wellbore 12 into the earth 16. In some instances, the fractures can be initiated by the fluid exiting from the jet sub 226 as described in U.S. Pat. No. 5,765,642.

After the fracturing operations are complete, the working string 224 can be withdrawn from the wellbore 12 or moved to another illustrative window casing 200 to perform perforating and/or fracturing operations on the other illustrative window casings. If so desired, the sleeve member 212 can be moved to the closed position prior to withdrawing the working string 224 from the wellbore 12 or prior to moving to another illustrative window casing 200. If multiple window casings 200 are provided in the wellbore 12, desired ones or all of the window casings 200 can be moved to the closed position prior to withdrawing the working string 224 from the wellbore 12. Thereafter, a working string 224 including at least the sleeve operating tool 222 can be run into the wellbore 12 to selectively open and close the window casings 200.

By selectively opening and closing different sleeve members 212, one or more intervals of interest 18 can be isolated. For example, to produce from or inject fluids into a given interval of interest 18 and no others, only those sleeve members 212 corresponding to the interval of interest 18 are set in the open position. To produce from or inject fluids into multiple intervals of interest 18, the sleeve members 212 corresponding to the desired intervals of interest 18 are set in the open position, and the others are set to the closed position.

Of note, the operations of the above-described method need not be performed in the order depicted in FIGS. 2A-D. Also, steps can be added or omitted. For example, if the apertures 216 and apertures 218 are provided in the illustrative window casing 200 prior to being installed in the wellbore 12, the perforating operations can be omitted. In some instances, the fracturing operations may be omitted.

Although several illustrative implementations of the invention have been described in detail above, those skilled in the art will readily appreciate that many other variations and modifications are possible without materially departing from the concepts described herein. Accordingly, other implementations are intended to fall within the scope of the invention as defined in the following claims. 

1. A method of treating a wellbore, comprising: perforating at least one of a casing or a sleeve proximate to the casing in a wellbore to form one or more apertures therein, wherein the apertures are operable to allow passage of fluids between an interior of the casing and earth surrounding the wellbore; and moving the sleeve to close one or more of the apertures and substantially seal against passage of fluids therethrough.
 2. The method of claim 1 wherein the casing comprises one or more apertures formed prior to the perforating operation.
 3. The method of claim 2 wherein moving the sleeve to close one or more of the apertures comprises moving the sleeve to close one or more of the apertures formed prior to the perforating operation.
 4. The method of claim 1 further comprising fracturing a formation surrounding the wellbore through one or more of the apertures prior to moving the sleeve.
 5. The method of claim 4 wherein fracturing the formation comprises flowing a fracturing fluid to a location proximate the one or more apertures though an interior of a working string.
 6. The method of claim 4 wherein fracturing the formation comprises flowing a fracturing fluid to a location proximate one or more apertures through an annulus between a working string and the wall of the wellbore.
 7. The method of claim 1 wherein perforating the wall of the wellbore comprises directing fluid at the wall of the wellbore to form one or more apertures therein.
 8. The method of claim 7 further comprising directing fluid through the one or more apertures into a formation surrounding the wellbore to fracture the formation.
 9. The method of claim 1 wherein perforating at least one of the casing or the sleeve comprises perforating the casing without perforating the sleeve.
 10. The method of claim 1 wherein: perforating comprises perforating at least one of the casing or a first sleeve at a first location; the method further comprises perforating at least one of the casing or a second sleeve at a second location axially spaced from the first location to form one or more apertures therein, wherein the apertures are operable to allow passage of fluids between an interior of the casing and earth surrounding the wellbore; and moving the sleeve to close one or more of the apertures and substantially seal against passage of fluids therethrough comprises moving at least one of the first sleeve or the second sleeve to close one or more of the apertures and substantially seal against passage of fluids therethrough.
 11. The method of claim 10 further comprising moving at least one of the first sleeve or the second sleeve to allow passage of fluids between the interior of the casing and the earth surrounding the wellbore.
 12. The method of claim 10 further comprising leaving the second sleeve positioned to allow passage of fluids between the interior of the casing and the earth surrounding the wellbore.
 13. A method of treating a wellbore, comprising: forming one or more perforations through a casing in the wellbore; flowing fluid through one or more of the perforations to fracture a formation about the wellbore; and closing at least one of the perforations to substantially seal against passage of fluids therethrough.
 14. The method of claim 13 wherein forming one or more perforations through the casing comprises: positioning a downhole tool in the wellbore; and flowing fluid out of an aperture of the downhole tool, wherein the aperture is adapted to direct the fluid at the casing.
 15. The method of claim 14 wherein flowing fluid through one or more of the perforations to fracture the formation further comprises flowing fluid out of an aperture of the downhole tool to draw fracturing fluid proximate the downhole tool through one or more of the perforations and into the formation.
 16. The method of claim 15 wherein forming one or more perforations and fracturing the formation are performed without substantially longitudinally re-positioning the downhole tool in the wellbore.
 17. The method of claim 13 wherein closing at least one of the perforations comprises moving a sleeve to cover the at least one perforation.
 18. The method of claim 13 further comprising: forming one or more perforations through the casing in the wellbore at a second location longitudinally spaced from the first mentioned location; and flowing fluid through one or more of the perforations at the second location to fracture the formation about the wellbore.
 19. A well completion system, comprising: a casing adapted for insertion into the well; a downhole tool adapted for insertion into the casing and operable to form one or more perforations through the casing, wherein the one or more perforations are adapted to allow passage of fluid through the casing; and a sleeve carried by the casing and movable to cover and substantially prevent passage of fluid through one or more of the perforations.
 20. The well completion system of claim 19 wherein the downhole tool is adapted to direct fluid through one or more of the perforations to draw fracturing fluid proximate the downhole tool through one or more of the perforations and into the formation to fracture the formation.
 21. The well completion system of claim 19 wherein the downhole tool is adapted to move the sleeve to cover and substantially prevent passage of fluid through one or more of the perforations. 